Crawler assembly

ABSTRACT

A crawler assembly aiming at preventing bogie wheels from detaching from a track, stabilizing the running of the bogie wheels and making it possible to use the crawler assembly for an endless rubber belt having core bars embedded therein and also for an endless iron caterpillar. The crawler assembly comprises a plurality of outer-flanged bogie wheels (3) each having flange portions (3b, 3b&#39;) formed on both outer sides of a central inner wheel portion so as to project radially; and an endless rubber belt 4&#39; having core bars (10) embedded therein and which is wound round outside these outer-flanged bogie wheels, or an endless iron crawler track (1) provided with shoe links, and arrangement is made such that in the case of the rubber belt (4) the rolling surfaces of the flange portions of each of the outer-flanged bogie wheels are kept in contact with exposed stepped shoulder portions (13a, 13b, 13a&#39;, 13b&#39;) of the core bars (10), whilst in the case of the iron crawler track the rolling surfaces (3a) of the outer-flanged bogie wheels are kept in contact with the upper surfaces of the shoe links.

TECHNICAL FIELD OF THE INVENTION

This invention relates to a crawler assembly, and more particularly to arubber crawler assembly for use in earth moving machines or vehicleshaving endless rubber belts with core bars embedded therein.

BACKGROUND ART OF THE INVENTION

As the undercarriage of earth moving machines or vehicles, an ironcrawler track 1 has mainly been used, and as means for running andturning such a track, center-flanged bogie wheels 2 as shown in FIG. lAand outer-flanged bogie wheels 3 as shown in FIG. lB are used.

In recent years, endless rubber belts 4 have come to be used partially.In combination with such rubber belts, center-flanged bogie wheels 2 asshown in FIG. 2A and outer-flanged bogie wheels 5 as shown in FIG. 2Bare used. The center-flanged bogie wheels 2 as shown in FIG. 2A can beused for both iron crawler tracks and rubber belts, and therefore alarge merit in terms of production cost reduction is obtained.

However, outer wheels 5a, 5a of the outer-flanged bogie wheels 5 asshown in FIG. 2B are not suitable for use with iron crawler tracks, andtherefore combined use of them cannot be made. In FIGS. 2A and 2B,reference numeral 6 denotes a core bar, and 7 steel cords embedded inthe rubber belt 4 so as to extend in the peripheral direction.

Hereupon, in case the rubber belts 4 are used in an earth movingvehicle, since the center-flanged bogie wheel (FIG. 2A) is kept inrolling contact with the top surfaces m of the central projections,vibration occurs on and along discontinuous surface between theadjoining bogie wheels, or when the rubber belt climbs over obstaclessuch as stone or the like such a phenomenon as inward bending of thebelt occurs, and at that time the spacing between the centralprojections of adjoining core bars is widened thus causing a dropping ofthe bogie wheels therein, and when the bogie wheels come out again, thecentral projections are kicked hard by the bogie wheels therebydetaching the core bars themselves from the rubber belts 4, and henceimpairing the durability thereof.

To prevent the occurrence of such a phenomenon, it is contemplated toform the central projections of the core bars in "T" shape and increasethe length f of the central projections as shown in FIG. 12A. However,if the length f is increased, then since the inner peripheral surface ofthe crawler at places where it is wound around a sprocket 8, theadjoining central projections strike against each other as shown by "g".Therefore, the length f of the central projection cannot be increasedbeyond a certain limit so that there is a limit in measures for reducingvibration and preventing the rubber belts from bending inwardly.

In contrast thereto, the outer-flanged bogie wheels (FIG. 2B) are keptin rolling contact on the inner peripheral surfaces of the rubber belts,and so the rolling contact surfaces of the bogie wheels are continuous.Therefore, the aforementioned problem does not occur, and vibration ofthe rubber belts can be reduced considerably. However, the bogie wheelsof this type cannot be used for iron crawler tracks, and also since thebogie wheels are kept in direct contact with the surfaces of the rubberbelts, "pitting phenomenon" (like water-eczema) will occur on thesurfaces of the rubber belts kept in contact with the bogie wheels,thereby impairing the durability of the rubber belts.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-mentionedcircumstances in the prior art and has for its object to provide arubber crawler assembly having core bars embedded therein which arecapable of preventing bogie wheels from detaching from the endlesstrack, stabilizing the rolling of the bogie wheels, reducing vibrationof the endless track, and also improving the durability of the endlessrubber belts themselves.

Another object of the present invention is to provide a crawler assemblywhich can be used for both rubber crawlers using endless rubber beltsand endless iron crawler tracks.

A still further object of the present invention is to provide a crawlerassembly which is capable of reducing considerably wear-down of thecentral projections of the core bars, thereby minimizing the lateralswing of the bogie wheels during running of the endless track, and hencepreventing the bogie wheels from detaching from the endless track.

To achieve the above-mentioned objects, according to a first aspect ofthe present invention, there is provided a crawler assembly comprising:a plurality of outer-flanged bogie wheels each having flange portionsformed on both outer sides of a central inner wheel portion thereof soas to project radially; and an endless rubber belt having core bar meansembedded therein and which is wound round outside these outer-flangedbogie wheels, or an endless iron crawler track provided with shoe linkmeans, wherein the arrangement is made such that in the case of therubber belt the rolling surfaces of the flange portions of each of theouter-flanged bogie wheels are kept in contact with exposed steppedshoulder portions of the core bar means, whilst in the case of the ironcrawler track the rolling surfaces of the central inner wheel portionsof the outer-flanged bogie wheels are kept in contact with the uppersurfaces of the shoe link means.

To achieve the above-mentioned objects, according to a second aspect ofthe present invention, there is provided a crawler assembly as set forthin the first aspect wherein the core bar means of the rubber belt iscomprised of a plurality of core bar members embedded in the rubber beltat predetermined intervals with one another along the peripheraldirection of the rubber belt and in such a manner that each of the corebars is partially exposed from the inner periphery of the rubber belt.

To achieve the above-mentioned objects, according to a third aspect ofthe present invention, there is provided a crawler assembly as set forthin the second aspect wherein parallel grooves are formed transverselywidthwise between the mutually adjacent core bar members in the innerperipheral surface of the rubber belt.

To achieve the above-mentioned objects, according to a fourth aspect ofthe present invention, there is provided a crawler assembly as set forthin the second aspect wherein each of the core bar members comprises apair of central projections standing upright in opposed relationshipwith each other on both sides of a central connecting portion, left-handand right-hand horizontal portions projecting integrally from thesecentral projections on the opposite sides of the central connectingportion, and stepped shoulder portions formed in parallel with eachother in the boundaries between the left-hand and right-hand horizontalwing portions and the pair of central projections, respectively, thestepped shoulder portions projecting outwardly from the front and rearends of each of the horizontal wing portions, the stepped shoulderportions each having a substantially flat surface somewhat higher inlevel than the upper surface of each of the left-hand and right-handhorizontal wing portions.

According to a fifth aspect of the present invention, there is provideda crawler assembly as set forth in the fourth aspect wherein each pairof stepped shoulder portions of the core bar member have a recess formedin the intermediate portion thereof and having a predetermined length.

According to a sixth aspect of the present invention, there is provideda crawler assembly as set forth in the fifth aspect, wherein the lengthsof the upper surfaces of the front and rear stepped shoulder portionshaving the above-mentioned recess formed therebetween are different, andthe arrangement of the upper surfaces of the front and rear steppedshoulder portions on the side of the left-hand horizontal wing portionis reverse to that of the upper surfaces of the front and rear steppedshoulder portions on the side of the right-hand horizontal wing portion.

According to a seventh aspect of the present invention, there isprovided a crawler assembly as set forth in the sixth aspect whereineither one of the front and rear stepped shoulder portions on the sideof the left-hand wing portion and the other one out of the front andrear stepped shoulder portions on the side of the right-hand horizontalwing portion are omitted.

According to an eighth aspect of the present invention, there isprovided a crawler assembly as set forth in the fourth aspect whereinthe pair of central projections of the core bar member are formed out ofphase in front and rear about the central point of the core bar member,and also the stepped shoulder portions are formed only on either one ofthe front or rear side reverse to the biased side of each of the centralprojections.

According to a ninth aspect of the present invention, there is provideda crawler assembly as set forth in the fourth aspect wherein anintermediate stepped shoulder portion is formed integrally with thelower portion of the end face of each of the pair of central projectionson the side of each of the stepped shoulder portions, each of theintermediate stepped portions having a height which is intermediatebetween the height of the top surface of each of the central projectionsand that of the upper surface of each of the stepped shoulder portions,the skirt portion of each of the intermediate stepped shoulder portionsjoining the upper surface of each of the stepped shoulder portions

According to a tenth aspect of the present invention, there is provideda crawler assembly as set forth in the ninth aspect wherein each of theintermediate stepped shoulder portion is formed partially in the centralzone of the end face of each of the central projections.

The above-mentioned and other objects, aspects and advantages of thepresent invention will become apparent to those skilled in the art bymaking reference to the following description and the accompanyingdrawings in which preferred embodiments incorporating the principles ofthe present invention are shown by way of example only.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. lA, lB, 2A and 2B are schematic, transverse sectional viewsshowing embodiments of prior art crawler assemblies, respectively;

FIG. 3 is a schematic, perspective view of a core bar used in a crawlerassembly of the present invention;

FIG. 4 is a fragmentary, perspective view showing a condition whereinthe core bars shown in FIG. 3 are embedded in a rubber belt proper;

FIGS. 5A, 5B and 5C show conditions wherein bogie wheels are kept incontact with the rubber belt having the core bars embedded therein; FIG.5A is a schematic, transverse sectional view showing such a condition inthe case of a rubber crawler assembly, while FIG. 5B is a schematic,longitudinal sectional view taken along line B--B; FIG. 5C is aschematic, transverse sectional view showing such a condition in thecase of a crawler track made of iron;

FIGS. 6, 8 and 10 are plan views showing other embodiments of the corebar;

FIGS. 7, 9 and 11 are fragmentary plan views, respectively, showingconditions wherein the core bars as shown in FIGS. 6, 8 and 10,respectively are embedded in the rubber belt propers;

FIGS. 12A and 12B are schematic longitudinal sectional views,respectively, showing a crawler assembly wound round a sprocket portion;FIG. 12A shows such a condition in the case of the prior art example,while FIG. 12B shows such a condition in the case of the embodiment ofthe present invention;

FIGS. 13A and 13B are schematic, transverse sectional views,respectively, showing floating conditions of the bogie wheel in case therubber belt having the core bars embedded therein is tilted; FIG. 13Ashows such a condition in the case of the prior art example, while FIG.13B shows such a condition in the case of the embodiment of the presentinvention;

FIG. 14 is an explanatory view showing wear-down condition of thecentral projection of the core bar in the prior art rubber crawlerassembly when it is running, looking from the longitudinal direction ofthe rubber belt;

FIGS. 15 and 16 are schematic, perspective views showing further twoembodiments of the core bar;

FIG. 17A is a fragmentary, transverse sectional view showing apositional relationship between the core bar and the outer flange bogiewheel in a crawler assembly having the core bars as shown in FIGS. 15and 16 embedded therein when it is running;

FIG. 17B is an explanatory view showing wear-down condition of thecentral projection of the core bar in the rubber crawler assembly of thepresent invention when it is running, looking from the longitudinaldirection of the rubber belt; and

FIG. 18 is a transverse sectional view of a still further embodiment ofthe rubber belt having the core bars embedded therein according to thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described below in detail by way ofseveral embodiments with reference to the accompanying drawings. (FIGS.13 to 18)

FIRST EMBODIMENT

FIG. 3 shows a core bar 10 for use in a rubber crawler according to thepresent invention. Reference numerals 11 and 11' denote left-hand andright-hand wing portions, and 12 and 12' a pair of central projectionswhich are formed upright in opposed relationship and at predeterminedintervals in the central area of the core bar 10. The configuration ofthe core bar of the present invention is similar to those of the priorart examples. The core bar 10 has stepped shoulder portions 13a, 13b and13a' and 13b' formed integrally therewith by projecting each of thefront and rear edge portions in the boundary between the outer surfacesof the central projection 12 and 12' and the left-hand and right-handwing portions 11 and 11', respectively, by a predetermined length in thewidthwise direction of the wing portions in such a manner that the uppersurfaces of the stepped shoulder portions 13a, 13b and 13a' and 13b' aregenerally flat and somewhat higher than the left-hand and right-handwing portions 11, 11', and recesses 14 and 14' formed between thestepped shoulder portions 13a and 13b and 13a' and 13b', respectively,are lower than the upper surfaces.

Thus, the core bars 10 having the above-mentioned configuration areembedded in a rubber belt 4 in such a way as to partially expose theupper surfaces of the stepped shoulder portions 13a,13b,13a' and 13b'from the inner periphery of the rubber belt as shown in FIG. 4. Further,in FIG. 4, reference numeral 15 denotes a hole adapted to engage with atooth of a sprocket 8, 16 a steel cord embedded in the rubber belt 4, 17a groove formed between the adjoining core bars in parallel with thesame, and 1 a central connecting portion.

FIGS. 5A, 5B and 5C show conditions of the crawler assembly in usewherein each of bogie wheels 3 is of an outer flange type, and its innerperipheral rolling surface 3a and outer peripheral surfaces of its outerflanges 3b, 3b' are brought into contact in turn with top surfaces 12aand 12a' of the central projections 12 and 12' and the stepped shoulderportions 13a,13b, 13a' and 13b'. Stating more concretely, when the bogiewheel 3 is located on the top surfaces 12a and 12a' of the centralprojections 12 and 12', the rubber belt 4 runs 25 while the top surfaces12a and 12a' of the central projections 12 and 12' are being pushed bythe inner peripheral surface 3a, while the bogie wheel 3 is not locatedat such a position, the rubber belt 4 runs while the stepped shoulderportions 13a and 13a' or 13b and 13b' are being pushed by the outerflange portions 3b and 3b' .

In that case, since the extent X of each of the top surfaces 12a, 12a'of the central projections 12, 12' covers the portion of the rubber beltproper having a high rigidity, when the bogie wheel 3 is located on thetop surfaces 12a, 12a'it is subjected to a high stress, whilst since theextent y of each of the top surfaces of the stepped shoulder portions13a,13b' and 13a' and 13b' covers the portion of the belt proper havinga rigidity less than that of the extent y, the bogie wheel 3 issubjected to a smaller stress. Therefore, the width V of each of theouter flanges 3b and 3b' which come into contact with the steppedshoudler portions can be set at a comparatively small value.

During the above-mentioned running of the rubber belt, when each of thebogie wheels 3 is located on the top surfaces of the central projections12 and 12', the outer flanges 3b and 3b' are located in the recesses 14and 14', respectively, formed between the stepped shoulder portions 13aand 13b and between the stepped shoulder portions 13a' and 13b' innon-contact condition.

FIG. 5C is a sectional view of the iron crawler track in runningcondition wherein the outer peripheral surface 3a of the central innerwheel portion of the bogie wheel 3 is kept in contact with the shoelink.

SECOND EMBODIMENT

FIG. 6 shows another embodiment of the core bar wherein the length l ofthe stepped shoulder portion 13a is shorter than the length l' of thestepped shoulder portion 13b, whilst the length of the stepped shoulderportion 13a' is longer than the length of the stepped shoulder portion13b'; that is; at the left and right positions outside the centralprojection 12 and 12', the long and short stepped shoulder portions arelocated in staggered relationship. FIG. 7 is a plan view showing suchcore bars embedded in a rubber belt proper. In this case, the longstepped shoulder portions 13b and 13a' and the short stepped portions13a and 13b' are located alternately or in staggered relationship in thelengthwise direction of the core bar.

THIRD EMBODIMENT

FIG. 8 shows a further embodiment of the core bar wherein the shortstepped shoulder portions of the embodiment shown in FIG. 6 are omitted,while FIG. 9 is a plan view showing such core bars embedded in a rubberbelt proper.

In this third embodiment, as in the case of the second embodiment, whenthe core bars 10 are embedded in the rubber belt proper, the distancebetween the stepped shoulder portions of the adjoining core bars 10, 10can be reduced wherever practicable.

FOURTH EMBODIMENT

While in the above-mentioned first, second and third embodiments thecentral projections 12, 12' of the core bars are formed in opposed andparallel relationship in the central portion thereof, in this fourthembodiment the central projection 12 and 12' are located in parallel andstaggered or out of phase relationship with each other, as shown in FIG.10. By such an arrangement, the length of projection of the steppedshoulder portions can be increased as shown in FIG. 11 so that thespacing j between the lengthened stepped shoulder portion of one of theadjacent core bars 10 and the central projection of the other core bar10 can be reduced, and also the spacing k between the right-hand steppedshoulder portion of one of the adjacent core bars 10 and the left-handstepped shoulder portion of the other core bar 10 can be reduced (or setto zero) wherever practicable. Thus, vibration of the rubber belt duringrunning can be reduced further.

Since the crawler assembly of the present invention is configured asmentioned above, the bogie wheel can be used for both the iron crawlertrack and the rubber belt having the core bars embedded therein.

Further, in case the rubber belt having the core bars embedded thereinis used, the distance between the surfaces of the core bar which arekept in rolling contact with the bogie wheel; that is, the top surfacesof the stepped shoulder portions 13a,13b, 13a' and 13b' of the core barand steel cords 16 can be set comparatively smaller that in the case ofthe prior art example. Therefore, as shown in FIG. 12A (prior artexample) and FIG. 12B (the embodiment of the present invention), d>d'and e>e'.

Therefore, the occurrence of such a phenomenon as inward bending of therubber belt when it climbs over obstacles such as stone or the like canbe prevented so that vibration of the rubber belt can be reduced therebyimproving the stability thereof during running.

Further, the compressibility of the crawler assembly wound round thesprocket can be reduced, and also collision of the adjoining core barswith each other when the crawler assembly is wound round the sprocketcan be prevented, so that effective driving power transmission can beachieved. Further, at that time, the groove 17 serves to release thecompressive strain which occurs on the inner peripheral surface of therubber belt proper.

Still further, according to the present invention, since "puttingphenomenon" does not occur, the durability of the rubber belt isexcellent, and also since the outer flanges of the bogie wheel urgeagainst the stepped shoulder portions, the width V of each of the outerflanges of the bogie wheel (Refer to FIG. 5A) can be reduced.

Yet further, according to the present invention, since the recesses 14and 14' are defined between the stepped shoulder portions of the corebars, as shown in FIGS. 13A (prior art example) and 13B (presentinvention), the amount of "floating" or rising of the bogie wheel incase the rubber belt having the core bars embedded therein is tilted canbe reduced so that the affect of preventing the belt from being detachedfrom the bogie wheel can be enhanced.

Further, in the embodiment of the present invention as shown in FIG. 8,since there is no fear of the core bars colliding with each other in theportions of the crawler assembly wound round the sprocket, the length ofthe stepped shoulder portions 13b, 13a' can be increased sufficiently,so that the amount of dropping of the bogie wheel between the centralprojections of the adjoining bars can be reduced further, therebyenhancing the vibration preventing effect conspicuously.

Hereupon, in case the rubber belt having the core bars embedded thereinis used, there is a problem that during running of the rubber belt, whenthe outer flanges 3b (3b') of the outer-flanged bogie wheel 3 arerunning on the stepped shoulder portions K of the core bar 6, the outerend faces of the central projections P of the core bar which projectupwardly in the central zone of the rubber belt proper 4 are broughtinto contact with the left-hand and right-hand outer flange portions 3band 3b' of the outer-flanged bogie wheel 3, thus causing severewear-down of the upper marginal portions S of the outer end faces of thecentral projections P of the core bar 6.

Such quick wear-down of the upper marginal portions S is due to the factthat the distance D→C(=L) of movement of the bogie wheel 3 on the topsurfaces of the stepped shoulder portions K is equal to the distance orthe circular arc D→C' over which the outer peripheries of the outerflange portions (3b, 3b') are brought into contact with the top surfacesof the stepped shoulder portions K, while the difference between thelength F→E (which is equal to the above-mentioned length L) of theouter, upper marginal portions of the central projections P and theinside distance F→E'(=L') of the outer flange portions (3b, 3b') whichare brought into contact with the outer, upper marginal portions islarge.

As a result, the vibration of the endless track will increase graduallyso that the bogie wheels become liable to detach from the rubber belt.

Embodiments of the core bar which have been improved to eliminate theabove-mentioned disadvantage are shown in FIGS. 15 and 16.

FIG. 15 is a perspective view of an improved core bar 10' according tothe present invention wherein intermediate stepped shoulder portions 18,18 are formed between the central projections P, P which stand uprightin the central zone and stepped shoulder portions K, K on both sides ofthe core bar.

FIG. 16 is a modification of the embodiment of core bar shown in FIG.15. While in the embodiment shown in FIG. 15 the intermediate steppedshoulder portions 18, 18 are formed along the whole outer end faces ofthe central projections P, P, a core bar 10" in this embodiment hasintermediate stepped shoulder portions 18', 18' formed only along thecentral portions of the outer end surfaces of the central projections P,P.

FIG. 17A is a fragmentary, transverse sectional view showing a conditionwherein the rubber belt having the core bars 10' of the above-mentionedconfiguration embedded therein is located opposite to the outer-flangedbogie wheel 3 when the belt is running, while FIG. 17B is an explanatoryview showing such condition in longitudinal section.

In the rubber crawler assemblies having the modified core bars as shownin FIGS. 15 and 16, respectively, embedded therein, when the bogiewheels 3 are rolling, the inner peripheral surfaces of the outer flangeportions 3b (3b') are located opposite to the intermediate steppedshoulder portions 18 (18') with an appropriate clearance kepttherebetween.

Thus, since the intermediate stepped shoulder portions 18 are located atlower positions near the surfaces of the stepped shoulder portions K onwhich the bogie wheel runs, during running of the crawler assembly, thedifference between the length M-N (which is equal to the above-mentionedlength L) of the upper marginal portions of the sides of theintermediate stepped shoulder portions 18 and the inside distanceM-N'(L") of the outer flange portions 3b (3b') which are locatedopposite to the upper marginal portions is limited (L≈L') as comparedwith FIG. 14 (prior art example, so that the amount of wear-down of theoppositely located portions can be reduced substantially.

In this case, it is also possible to locate the inner peripheralsurfaces of the outer flange portion 3b (3b') opposite to the uppermarginal portions G of the central projections P, P in addition to theintermediate stepped shoulder portions 18 (18'). Since the wear-down ofthe intermediate stepped shoulder portions 18 (18') is reduced, thewear-down of the upper marginal portions G can be reduced in likemanner.

Further, it is not always necessary to provide the intermediate steppedshoulder portions 18, and instead widthwise reduced stepped shoulderportions 18', 18' may be provided as shown in FIG. 16 to obtain the sameeffect.

FIG. 18 shows a still further embodiment of the rubber belt having thecore bars embedded therein according to the present invention. Accordingto this embodiment, steel cords 19 are embedded between the upperportion of the rubber belt 4 having the core bars 10 embedded therein;that is, the upper surface of the rubber belt and the left-hand andright-hand wing portions of the core bar 10.

What is claimed is:
 1. A crawler assembly comprising: a plurality ofouter-flanged bogie wheels each having flange portions formed on bothouter sides of a central inner wheel portion thereof so as to projectradially, said flange portions having rolling surfaces; and an endlessrubber belt having core bar means embedded therein and which is woundaround the outside of said outer-flanged bogie wheels, wherein thearrangement is made such that the rolling surfaces of the flangeportions of each of said outer-flanged bogie wheels are kept in contactwith exposed stepped shoulder portions of said core bar means, andwherein the core bar means of said rubber belt is comprised of aplurality of mutually adjacent core bar members embedded in the rubberbelt at predetermined intervals with one another along the peripheraldirection of the rubber belt and in such a manner that each of the corebars is partially exposed from the inner periphery of the rubber belt.2. A crawler assembly as claimed in claim 1, wherein parallel groovesare formed transversely widthwise between said mutually adjacent corebar members in the inner peripheral surface of said rubber belt.
 3. Acrawler assembly as claimed in claim 1, wherein each of said core barmembers comprises a pair of central projections standing upright inopposed relationship with each other on both sides of a centralconnecting portion, left-hand and right-hand horizontal wing portionsprojecting integrally from these central projections on the oppositesides of said central connecting portion, and stepped shoulder portionsformed in parallel relationship with each other in the boundariesbetween the left-hand and right-hand horizontal wing portions and saidpair of central projections, respectively, the stepped shoulder portionsprojecting outwardly from the front and rear ends of each of thehorizontal wing portions, said stepped shoulder portions each having asubstantially flat surface somewhat higher in level than the uppersurface of each of said left-hand and right-hand horizontal wingportions.
 4. A crawler assembly as claimed in claim 3, wherein each pairof stepped shoulder portions of said core bar member have a recessformed in the intermediate portion thereof and having a predeterminedlength.
 5. A crawler assembly as claimed in claim 4, wherein the lengthsof the upper surfaces of the front and rear stepped shoulder portionshaving said intermediate recess formed therebetween are different, andthe arrangement of the upper surfaces of the front and rear steppedshoulder portions on the side of the left-hand horizontal wing portionis reverse to that of the upper surfaces of the front and rear steppedshoulder portions on the side of the right-hand horizontal wing portion.6. A crawler assembly as claimed in claim 5, wherein the front steppedshoulder portion on the side of said left-hand horizontal wing portionand the rear stepped shoulder portion on the side of said right-handhorizontal wing portion are omitted.
 7. A crawler assembly as claimed inclaim 3, wherein the pair of central projections of said core bar memberare formed out of phase in front and rear about the central point of thecore bar member, creating a biased side of each of said centralprojections, and also said stepped shoulder portions are formed only oneither one of the front or rear side reverse to the biased side of eachof the central projections.
 8. A crawler assembly as claimed in claim 3,wherein an intermediate stepped shoulder portion is formed integrallywith the lower portion of the end face of each of said pair of centralprojections on the side of each of said stepped shoulder portions, eachof the intermediate stepped shoulder portions having a height which isintermediate between the height of the top surface of each of thecentral projections and that of the upper surface of each of saidstepped shoulder portions, the skirt portion of each of the intermediatestepped shoulder portions joining the upper surface of each of saidstepped shoulder portions.
 9. A crawler assembly as claimed in claim 8,wherein each of said intermediate stepped shoulder portions is formedpartially in the central zone of the end face of each of said centralprojections.
 10. A crawler assembly as claimed in claim 1, wherein itfurther comprises steel cords embedded between the upper surface of saidrubber belt and said core bar means.
 11. A crawler assembly as claimedin claim 5, wherein the rear stepped shoulder portion on the side ofsaid left-hand horizontal wing portion and the front stepped shoulderportions on the side of said right-hand horizontal wing portion areomitted.